Sleep is a natural, periodic behavioral state during which the body rests itself and its physiological powers are restored. It is characterized by a loss of reactivity to the environment. During sleep, certain physiological processes of both the body and the brain function differently than they do during alert wakefulness. Normal sleep consists of at least two quite different behavioral states: synchronized sleep, during which the electroencephalogram consists of slow waves of high amplitude, and desynchronized sleep (DS) or activated sleep characterized by rapid eye movements (REM sleep), in which the electroencephalogram pattern is characterized by waves of high frequency and low amplitude. Synchronized sleep is further characterized by slow and regular respiration, by relatively constant heart rate and blood pressure, and by a predominance of delta waves. Synchronized sleep usually consists of four stages, followed by a period of activated sleep. Each cycle lasts between 80 and 120 minutes. In contrast, desynchronized sleep is further characterized by irregular heart rate and respiration, periods of involuntary muscular jerks and movements, and a higher threshold for arousal. Periods of desynchronized sleep last from 5-20 minutes and occur at about 90 minute intervals during a normal night's sleep.
Sleep disorders include sleep deprivation and paroxysmal sleep, i.e., narcolepsy. There has been no known pharmacological method for promoting or inhibiting the initiation of sleep or for maintaining the sleeping or waking state.
Cerebrospinal fluid (liquor cerebrosinalis) is a clear, colorless fluid that circulates within the four ventricles of the brain and the subarachnoid spaces surrounding the brain and spinal cord Cerebrospinal fluid originates as an ultrafiltrate of the blood secreted by the choroid plexus in the lateral third and fourth ventricles. Cerebrospinal fluid is also sometimes called neurolymph. After passing through the four ventricles and the subarachnoid spaces, cerebrospinal fluid is largely resorbetd into the venous system via the arachnoid villi. Cerebrospinal fluid serves as a medium for the removal of catabolites, excretions, and waste materials from the tissues bathed by it. To date, no factor derived from cerebrospinal fluid has been reported to correlate with sleep deprivation. What is needed is a method for analyzing cerebrospinal fluid for identifying a biochemical factor generated by subject that correlates with sleep deprivation.
Since the seminal discovery of prostaglandins, there has been increasing recognition of the role of fatty acids and their derivatives in important physiological processes, e.g., B. Samuelsson, Les Prix Nobel1982, pp. 153-174.
Cis-9,10-Octadecenoamide has been isolated from the cerebrospinal fluid of sleep-deprived cats and has been shown to exhibit sleep-inducing properties when injected into rats. Other fatty acid primary amides in addition to cis-9,10-octadecenoamide were identified as natural constituents of the cerebrospinal fluid of cat, rat, and man, indicating that these compounds compose a distinct family of brain lipids. Together, these results teach that fatty acid primary amides represent a new class of biological signalling molecules that can be employed for inducing subjects to sleep. Preferrers fatty acid primary amides include an alkyl chain having an unsaturation and are represented by the following formula: NH.sub.2 C (O) (CH.sub.2).sub.(6.gtoreq.n.ltoreq.11) CH.dbd.CH(CH.sub.2).sub.(8.gtoreq.n.ltoreq.5) CH.sub.3. Preferred soporific fatty acid primary amides have an unsaturation with a cis configuration within their alkyl chain. In addition to cis-9,10-octadecenoamide, other soporifically active fatty acid primary amides include cis-8,9-octadecenoamide, cis-11,12-octadecenoamide, and cis-13,14-docosenoamide.
Deutsch et al, Biochem. Pharmacol., 46:791 (1993) has identified an amidase activity which catalyzes both the hydrolysis and synthesis of arachidonylethanolamide (anandamide) from the membrane subcellular fractions taken from neuroblastoma, glioma cells and crude homogenates of rat brain tissues. The study detected the uptake and enzymatic breakdown of arachidonylethanolamide (anandamide) to arachidonic acid (and vice versa) from the homogenates of tissues from brain, liver, kidney and lung but not from rat heart and skeletal muscles.
The active membrane fraction which displayed this amidase activity was prepared by either homogenizing the desired cell line and subsequently subjecting the crude homogenate to density centrifugation or by taking the crude homogenates of rat brains and directly incubating them with anandamide.
The uptake and degradation of arachidonylethanolamide (anandamide) was assayed by incubation of [.sup.3 H]-anandamide (NEN, NET-1073, 210 Ci/mmol) in the cell culture medium. It was found, by liquid scintillation counting of the aqueous and organic phases, that arachidonic acid and anaiidamide distributed in the organic phase. Thus, the organic extract of the cell medium was subsequently visualized using thin-layer chromatography, sprayed with a surfaces autoradiograph enhancer (EN.sup.3 HANCE, Dupont) and exposed to X-ray film (Kodak X-OMAT AR) at -80.degree. C.
The serine protease inhibitor, phenylmethylsulfonyl fluoride at 1.5 mM concentration completely inhibited the amidase activity. Other inhibitors tested had little or no effect on the activity and included aprotinin, benzamidine, leupeptin, chymostatin and pepstatin.
In a second manuscript, Deusch et. al. (J. Biol Chem., 1994, 269, 22937) reports the synthesis of several types of specific inhibitors of anandamide hydrolysis and their ability to inhibit anandamide breakdown in vitro. Four classes of compounds were synthesized and include fatty acyl ethanolamides, .alpha.-keto ethanolamides, .alpha.-keto ethyl esters and trifluoromethyl ketones. The most effective class of compounds were the trifluoromethyl ketones and .alpha.-keto esters. The least potent inhibitors were the .alpha.-keto amides and saturated analogs of anandamide.
As an example, when anandamide is incubated with neuroblastoma cells, it is rapidly hydrolyzed to arachidonate but in the presence of the inhibitor arachidonyl trifluoromethyl ketone, there is a 5 fold increase of anandamide levels. The study infers that polar carbonyls such as those found in trifluoromethyl ketones, may form stabilized hydrates that mimic the tetrahedral intermediates formed during the reaction between the nucleophilic residue and the carbonyl group of anandamide. Deutsch suggests that the nucleophilic residue may be the active site of a serine hydroxyl in the hydrolytic enzyme.
This enzyme is classified as an amidase (EC #3.5) where the enzyme acts on carbon nitrogen bonds other than peptide bonds. The amidase activity is inhibited by the serine protease inhibitor, PMSF and the action of trifluoromethyl ketone inhibitors (and others) directly affect the hydrolytic activity of the enzyme. Furthermore, Deutsch suggests that anandamide is cleaved by a mechanism that involves an active site serine hydroxyl group.
What is needed is an identification of enzymes within the brain tissue which catalyze the degradation of soporific compound found in the cerebrospinal, for mediating the soporific activity of these compounds. What is needed is an identification of inhibitors for inhibiting the activity of enzymes which degrade soporific compounds of the type found in cerebrospinal fluid.